// Copyright (c) 2011 Google, Inc.

//

// Permission is hereby granted, free of charge, to any person obtaining a copy

// of this software and associated documentation files (the "Software"), to deal

// in the Software without restriction, including without limitation the rights

// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

// copies of the Software, and to permit persons to whom the Software is

// furnished to do so, subject to the following conditions:

//

// The above copyright notice and this permission notice shall be included in

// all copies or substantial portions of the Software.

//

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

// THE SOFTWARE.

//

// CityHash Version 1, by Geoff Pike and Jyrki Alakuijala

//

// This file provides CityHash64() and related functions.

//

// It's probably possible to create even faster hash functions by

// writing a program that systematically explores some of the space of

// possible hash functions, by using SIMD instructions, or by

// compromising on hash quality.

#include "city.h"

#include <algorithm>

using namespace std;

#define UNALIGNED_LOAD64(p) (*(const uint64*)(p))

#define UNALIGNED_LOAD32(p) (*(const uint32*)(p))

#if !defined(LIKELY)

#if defined(__GNUC__)

#define LIKELY(x) (__builtin_expect(!!(x), 1))

#else

#define LIKELY(x) (x)

#endif

#endif

// Some primes between 2^63 and 2^64 for various uses.

static const uint64 k0 = 0xc3a5c85c97cb3127;

static const uint64 k1 = 0xb492b66fbe98f273;

static const uint64 k2 = 0x9ae16a3b2f90404f;

static const uint64 k3 = 0xc949d7c7509e6557;

// Bitwise right rotate.  Normally this will compile to a single

// instruction, especially if the shift is a manifest constant.

static uint64 Rotate(uint64 val, int shift) {

  // Avoid shifting by 64: doing so yields an undefined result.

  return shift == 0 ? val : ((val >> shift) | (val << (64 - shift)));

}

// Equivalent to Rotate(), but requires the second arg to be non-zero.

// On x86-64, and probably others, it's possible for this to compile

// to a single instruction if both args are already in registers.

static uint64 RotateByAtLeast1(uint64 val, int shift) {

  return (val >> shift) | (val << (64 - shift));

}

static uint64 ShiftMix(uint64 val) {

  return val ^ (val >> 47);

}

static uint64 HashLen16(uint64 u, uint64 v) {

  return Hash128to64(uint128(u, v));

}

static uint64 HashLen0to16(const char *s, size_t len) {

  if (len > 8) {

    uint64 a = UNALIGNED_LOAD64(s);

    uint64 b = UNALIGNED_LOAD64(s + len - 8);

    return HashLen16(a, RotateByAtLeast1(b + len, len)) ^ b;

  }

  if (len >= 4) {

    uint64 a = UNALIGNED_LOAD32(s);

    return HashLen16(len + (a << 3), UNALIGNED_LOAD32(s + len - 4));

  }

  if (len > 0) {

    uint8 a = s[0];

    uint8 b = s[len >> 1];

    uint8 c = s[len - 1];

    uint32 y = static_cast<uint32>(a) + (static_cast<uint32>(b) << 8);

    uint32 z = len + (static_cast<uint32>(c) << 2);

    return ShiftMix(y * k2 ^ z * k3) * k2;

  }

  return k2;

}

// This probably works well for 16-byte strings as well, but it may be overkill

// in that case.

static uint64 HashLen17to32(const char *s, size_t len) {

  uint64 a = UNALIGNED_LOAD64(s) * k1;

  uint64 b = UNALIGNED_LOAD64(s + 8);

  uint64 c = UNALIGNED_LOAD64(s + len - 8) * k2;

  uint64 d = UNALIGNED_LOAD64(s + len - 16) * k0;

  return HashLen16(Rotate(a - b, 43) + Rotate(c, 30) + d,

                   a + Rotate(b ^ k3, 20) - c + len);

}

// Return a 16-byte hash for 48 bytes.  Quick and dirty.

// Callers do best to use "random-looking" values for a and b.

static pair<uint64, uint64> WeakHashLen32WithSeeds(

    uint64 w, uint64 x, uint64 y, uint64 z, uint64 a, uint64 b) {

  a += w;

  b = Rotate(b + a + z, 21);

  uint64 c = a;

  a += x;

  a += y;

  b += Rotate(a, 44);

  return make_pair(a + z, b + c);

}

// Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.

static pair<uint64, uint64> WeakHashLen32WithSeeds(

    const char* s, uint64 a, uint64 b) {

  return WeakHashLen32WithSeeds(UNALIGNED_LOAD64(s),

                                UNALIGNED_LOAD64(s + 8),

                                UNALIGNED_LOAD64(s + 16),

                                UNALIGNED_LOAD64(s + 24),

                                a,

                                b);

}

// Return an 8-byte hash for 33 to 64 bytes.

static uint64 HashLen33to64(const char *s, size_t len) {

  uint64 z = UNALIGNED_LOAD64(s + 24);

  uint64 a = UNALIGNED_LOAD64(s) + (len + UNALIGNED_LOAD64(s + len - 16)) * k0;

  uint64 b = Rotate(a + z, 52);

  uint64 c = Rotate(a, 37);

  a += UNALIGNED_LOAD64(s + 8);

  c += Rotate(a, 7);

  a += UNALIGNED_LOAD64(s + 16);

  uint64 vf = a + z;

  uint64 vs = b + Rotate(a, 31) + c;

  a = UNALIGNED_LOAD64(s + 16) + UNALIGNED_LOAD64(s + len - 32);

  z = UNALIGNED_LOAD64(s + len - 8);

  b = Rotate(a + z, 52);

  c = Rotate(a, 37);

  a += UNALIGNED_LOAD64(s + len - 24);

  c += Rotate(a, 7);

  a += UNALIGNED_LOAD64(s + len - 16);

  uint64 wf = a + z;

  uint64 ws = b + Rotate(a, 31) + c;

  uint64 r = ShiftMix((vf + ws) * k2 + (wf + vs) * k0);

  return ShiftMix(r * k0 + vs) * k2;

}

uint64 CityHash64(const char *s, size_t len) {

  if (len <= 32) {

    if (len <= 16) {

      return HashLen0to16(s, len);

    } else {

      return HashLen17to32(s, len);

    }

  } else if (len <= 64) {

    return HashLen33to64(s, len);

  }

  // For strings over 64 bytes we hash the end first, and then as we

  // loop we keep 56 bytes of state: v, w, x, y, and z.

  uint64 x = UNALIGNED_LOAD64(s);

  uint64 y = UNALIGNED_LOAD64(s + len - 16) ^ k1;

  uint64 z = UNALIGNED_LOAD64(s + len - 56) ^ k0;

  pair<uint64, uint64> v = WeakHashLen32WithSeeds(s + len - 64, len, y);

  pair<uint64, uint64> w = WeakHashLen32WithSeeds(s + len - 32, len * k1, k0);

  z += ShiftMix(v.second) * k1;

  x = Rotate(z + x, 39) * k1;

  y = Rotate(y, 33) * k1;

  // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.

  len = (len - 1) & ~static_cast<size_t>(63);

  do {

    x = Rotate(x + y + v.first + UNALIGNED_LOAD64(s + 16), 37) * k1;

    y = Rotate(y + v.second + UNALIGNED_LOAD64(s + 48), 42) * k1;

    x ^= w.second;

    y ^= v.first;

    z = Rotate(z ^ w.first, 33);

    v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);

    w = WeakHashLen32WithSeeds(s + 32, z + w.second, y);

    std::swap(z, x);

    s += 64;

    len -= 64;

  } while (len != 0);

  return HashLen16(HashLen16(v.first, w.first) + ShiftMix(y) * k1 + z,

                   HashLen16(v.second, w.second) + x);

}

uint64 CityHash64WithSeed(const char *s, size_t len, uint64 seed) {

  return CityHash64WithSeeds(s, len, k2, seed);

}

uint64 CityHash64WithSeeds(const char *s, size_t len,

                           uint64 seed0, uint64 seed1) {

  return HashLen16(CityHash64(s, len) - seed0, seed1);

}

// A subroutine for CityHash128().  Returns a decent 128-bit hash for strings

// of any length representable in an int.  Based on City and Murmur.

static uint128 CityMurmur(const char *s, size_t len, uint128 seed) {

  uint64 a = Uint128Low64(seed);

  uint64 b = Uint128High64(seed);

  uint64 c = 0;

  uint64 d = 0;

  int l = len - 16;

  if (l <= 0) {  // len <= 16

    c = b * k1 + HashLen0to16(s, len);

    d = Rotate(a + (len >= 8 ? UNALIGNED_LOAD64(s) : c), 32);

  } else {  // len > 16

    c = HashLen16(UNALIGNED_LOAD64(s + len - 8) + k1, a);

    d = HashLen16(b + len, c + UNALIGNED_LOAD64(s + len - 16));

    a += d;

    do {

      a ^= ShiftMix(UNALIGNED_LOAD64(s) * k1) * k1;

      a *= k1;

      b ^= a;

      c ^= ShiftMix(UNALIGNED_LOAD64(s + 8) * k1) * k1;

      c *= k1;

      d ^= c;

      s += 16;

      l -= 16;

    } while (l > 0);

  }

  a = HashLen16(a, c);

  b = HashLen16(d, b);

  return uint128(a ^ b, HashLen16(b, a));

}

uint128 CityHash128WithSeed(const char *s, size_t len, uint128 seed) {

  if (len < 128) {

    return CityMurmur(s, len, seed);

  }

  // We expect len >= 128 to be the common case.  Keep 56 bytes of state:

  // v, w, x, y, and z.

  pair<uint64, uint64> v, w;

  uint64 x = Uint128Low64(seed);

  uint64 y = Uint128High64(seed);

  uint64 z = len * k1;

  v.first = Rotate(y ^ k1, 49) * k1 + UNALIGNED_LOAD64(s);

  v.second = Rotate(v.first, 42) * k1 + UNALIGNED_LOAD64(s + 8);

  w.first = Rotate(y + z, 35) * k1 + x;

  w.second = Rotate(x + UNALIGNED_LOAD64(s + 88), 53) * k1;

  // This is the same inner loop as CityHash64(), manually unrolled.

  do {

    x = Rotate(x + y + v.first + UNALIGNED_LOAD64(s + 16), 37) * k1;

    y = Rotate(y + v.second + UNALIGNED_LOAD64(s + 48), 42) * k1;

    x ^= w.second;

    y ^= v.first;

    z = Rotate(z ^ w.first, 33);

    v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);

    w = WeakHashLen32WithSeeds(s + 32, z + w.second, y);

    std::swap(z, x);

    s += 64;

    x = Rotate(x + y + v.first + UNALIGNED_LOAD64(s + 16), 37) * k1;

    y = Rotate(y + v.second + UNALIGNED_LOAD64(s + 48), 42) * k1;

    x ^= w.second;

    y ^= v.first;

    z = Rotate(z ^ w.first, 33);

    v = WeakHashLen32WithSeeds(s, v.second * k1, x + w.first);

    w = WeakHashLen32WithSeeds(s + 32, z + w.second, y);

    std::swap(z, x);

    s += 64;

    len -= 128;

  } while (LIKELY(len >= 128));

  y += Rotate(w.first, 37) * k0 + z;

  x += Rotate(v.first + z, 49) * k0;

  // If 0 < len < 128, hash up to 4 chunks of 32 bytes each from the end of s.

  for (size_t tail_done = 0; tail_done < len; ) {

    tail_done += 32;

    y = Rotate(y - x, 42) * k0 + v.second;

    w.first += UNALIGNED_LOAD64(s + len - tail_done + 16);

    x = Rotate(x, 49) * k0 + w.first;

    w.first += v.first;

    v = WeakHashLen32WithSeeds(s + len - tail_done, v.first, v.second);

  }

  // At this point our 48 bytes of state should contain more than

  // enough information for a strong 128-bit hash.  We use two

  // different 48-byte-to-8-byte hashes to get a 16-byte final result.

  x = HashLen16(x, v.first);

  y = HashLen16(y, w.first);

  return uint128(HashLen16(x + v.second, w.second) + y,

                 HashLen16(x + w.second, y + v.second));

}

uint128 CityHash128(const char *s, size_t len) {

  if (len >= 16) {

    return CityHash128WithSeed(s + 16,

                               len - 16,

                               uint128(UNALIGNED_LOAD64(s) ^ k3,

                                       UNALIGNED_LOAD64(s + 8)));

  } else if (len >= 8) {

    return CityHash128WithSeed(NULL,

                               0,

                               uint128(UNALIGNED_LOAD64(s) ^ (len * k0),

                                       UNALIGNED_LOAD64(s + len - 8) ^ k1));

  } else {

    return CityHash128WithSeed(s, len, uint128(k0, k1));

  }

}